Mushroom cloud helps heart research

A mushroom cloud half a century ago has helped clear up a vital medical question: Can the heart make new cells and repair itself?

"I would say that in the heart field, that this is one of those important studies that is going to change the way that we think for a very long time," said Dr. Richard T. Lee, of Brigham and Women's Hospital in Boston.

Scientists solved the mystery by going back in time.

Until it was banned in 1963, nuclear weapons testing above ground produced slightly radioactive carbon dioxide gas all over the planet. It entered the food chain. So if you were alive then, the radioactive material ended up in your DNA.

Today's study found that - over time - the amount of radioactive carbon in the heart decreases, suggesting old muscle cells are being replaced by new ones. They estimate that by the time you reach 50, almost half the muscle cells in your heart have been replaced by new ones.